of wobcester



Patented Mar. 6,1928.

I "UNITED:- STATES-'PATENT' ioFFlcE.

JOHN A. ornsoN, `or WORCESTER, MAssAcrrUsnTTs., assitance To wYMAN-eonnon COMPANY, oir-WORCESTER, MASSACHUSETTS, A conrenATroN or MASSACHUSETTS.,

.six-THROW Foun-nnAmNG BALANcEn caANK SHAFT.

Application med May 1, 1925. sei-iai No.'a'wsa 7 rl`his invention'relates*to a. balanced crankshaft of the six-throw four-bearing type. It iswell understood that the ordinary six-v tlirow crankshaft. although accurately balanced against static'forces, is notbalanced against dynamic forces and that serious vibration occurs when the speed is increased above a definite minimum.

It is vthe object of my invention tov pro",

vide a construction byfkwhich a'A six-throw tour-bearing crankshaft may be accurately t balanced both statically and dynamically and .Without substantial increase in the cost of manufacture.

In thevpreferred 'embodiment of my inven tion, I provide counterweights on the single or straight cheeks adjacent the end shaft bearings,` so positioned and proportioned that they substantiallyoffsot certain of the unbalanced dynamic forces that act to throwr p theshait out of runningbalance. As it is` ,necessary that the v-shaft 'shall also be letty in static balance, I provide additional counterweights on the straight or single' cheeks adjacent the intermediate shaft bearings to restore the static balance.

Byplacing these counterweights iny ce1'-y tain definite angularrelations to the positions of the crank pins, kI am able toproduce a crankshaft which may be rotated at high speed Without noticeable vibration. y

)Vith these general objects in r View, my invention also relates to certain arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claim.

A preferred form of the invention v is shown in the drawings,in Which n Fig; 1r is a side lelevation of my improved crank-shaft with counterweights applied thereto; n f 4 Fig. 2 is an end view thereof; and

Figs. 3 and 10 inclusive are sectional elef vations taken along they section lines having corresponding numbers in Fig. 1. K

Referring to Fig. 1,L I havel Shown a balanced crankshaft having end shaft bearings 20 and 21 and intermediate shaft bearings 22 and 23. The Shaft is also provided with six crank pins 30, 31, 32, 33, 34`A and 35.

A Single or straight` cheek (Fig. 3) connects the shaft bearings'20 to the crank pin 30; ka curved or connecting cheek41 (Fig. 4) connects the crank pin30` to the crank pin 31; a Straight cheek42y (Fig. 5.)

f speed.'

coiuiects the cranlipin 3l to the intermediatc shaft bearing and a straight or'sin- -glecheck 43 (F (i) yconnects the intermedi-itcv shaft bcainig to the crank pin 32.

Similarly, a Straight cheek 44 (Fig. 7)

connects the crank pin 33 to theintermediate f described. n n l K n Referring particularly to the left half ,with counternfeiglits Which `will now be of the crankshaft, asvieWed in Fig. 1, I

provide the single ycheek 40 with a counter* Weight 5() Whichis so disposed that it sub-' stantially offsetsy certain of the unbalanced dynamic forces which vare generated in the left half of kthe crankshat'tas it is rotated upon its bearings 20 and 22 at relatively high The mass of the counterweight may. beso designed that it Will vcounterbalance merely ythe unbalanced forces. generated by the shaft itself, `or it may be increased to counterbalance a greater or less ypart of the forces generated by the connecting rod ends which move with the crank pins.`

Both the mass and the yangular position of tho counterweight 50 may be determined mathematically or graphically `for `any particular crankshaft underdefined conditions.

rIhe center ot' the counterweight is oifset angularly from the center line otthe cheek 4() at anA angle a Which varies Somewhat with conditions, but which may be`generally defined as not substantially greater than y 306 and not substantially less than 10o. In

.an average case, .such as isv shown in the drawings, the angle a is approximately 15"., n

` Having'determined the mass and the angular position of the counterweight 50, it

exactly 180 from the counterweight y50 in yorder that the static balance of the shaft mayv be maintained.

Corresponding counterweights 52 andv53 are providedL forthe right hand end of the shaft, these counterweights beingr similarly determined and positioned, and a particular description thereof being considered unnecessary.

The counterweights 50, 5l, 52 and may be constructed in any desired manner and may be secured to the crankshaftrby bolts or welding or in any other suitable manner. In the preferredforin of my invention, however, I forge the counterweights integrall with the cheeks 4th 43, 44 and 4T, as shown in the drawings, this construction being;r rendered possible by the forging;r process disclosed in the prior' patent to Larcher, No. 1.434215. issuedy Oct. 31, 1922.

- After careful and extended tests ot crankshafts constructed as above set forth. it has been shown that such crankshafts may be runat much higher speed than has been heretofore practical and thatl at such speeds no undesirable vibration occurs.

Having thus described my invention and the advantages thereof. I do not wish to be limited to the details herein disclosed otherwise than as setorth in the claims, but what I claim is -A six-throw four-bearing crankshaft, having two straight. single cheeks and one curved connecting cheek between each end bearing and its adjacent intermediate shaft bearing and having two straight single cheeks between the two intermediate shaft bearings, and having a counterweight applied to each single cheek adjacent the end shaft bearings and to each single cheek between the intermediate shaft bearings and adjacent thereto, the counter-weights adjacent the end shaft bearings substantially counterbalancing certain of' the unbalanced dynamic forces generated by high speed rotationl of the crankshaft, and the counterweights between the intermediate shaftl bearings maintaining r the static balance rof the shaft. the center line of each end counter-weight being offset from the projected center line of its supportingr crank cheek at an angle of approximately 15O in one direction, and the-intermediate counter'- weights being offset from their supporting,r crankv cheeks and disposed at an angle of substantially 18()O with respect to the enf] counterweights.

Inl testimony whereof I have hereunto atlixed' my signature.

JOHN A. OLDSON. 

